Technical Abstract:
The United States Government has targeted aggressive development of bioethanol as one route for decreasing oil dependence and lowering greenhouse gas emissions. Achieving future production targets depends on expanding feedstock sources beyond corn and towards lignocellulose. This is expected to include new low- input and high yielding energy crops. Utilizing dedicated energy crops allows for the possibility of breeding them for increased conversion efficiency to ethanol. In this study, the effect of reducing lignin content was evaluated for sugar and ethanol production in forage sorghum (Sorghum bicolor (L.)). The sample set included wild-type and brown midrib mutants for reduced lignin contents. The mutants had reduced lignin contents compared to the wild-type, but did not vary significantly in carbohydrates. The set was treated with dilute-acid, washed, and the residual cellulose hydrolyzed with commercial cellulase. Extraction of glucose was negatively correlated with lignin content. Samples were again treated with dilute-acid, but this time the whole hydrolysate was neutralized and converted to ethanol using cellulases in combination with Saccharomyces yeast. The ethanol yield was also determined to be negatively correlated with lignin content. These results suggest that breeding for reduced lignin can lead to improved ethanol yields. Currently, selected samples from this set are being evaluated for ethanol production following pretreatment at higher temperatures under alkaline conditions to obtain higher ethanol yields.